Pipe coupling



FIG. 1 is an isometric view of our design for a pipe coupling;

FIG. 2 is a front view thereof, the rear view being a mirror image thereof;

FIG. 3 is a left side view thereof, the right side view being a mirror image thereof;

FIG. 4 is a top view thereof; and,

FIG. 5 is a bottom view thereof.

The broken lines depict portions of the pipe coupling that form no part of the claimed design. 

CLAIM The ornamental design for a pipe coupling, as shown and described. 